Something I've been thinking about is how much it bothers me that transmascs and trans men are never considered authorities on our own experiences. It's a kind of testimonial injustice. Someone else always thinks that they must know better than we do. They don't even stop to consider it: They see a trans man say something about his own life that goes against their preconceived notions and simply jump to correct him, thoughtlessly, because obviously he is wrong. The idea that we have interiority, intelligence, the ability to recognize and describe our lives, is not so much rejected as it is never even on the table to begin with. It is a particular kind of dehumanization, I think, to deny someone the ability to speak authoritatively on their own experiences.
I have had other trans people tell me to my face, flatly, that something I described (related to being transmasc) did not happen. It is straightforwardly an accusation of lying, but it's rarely phrased that way. Instead it's usually posed as a challenge to the idea that I could possibly have any idea what I'm talking about. "Are you sure that really happened?" in response to recounting an instance of transphobia, or "Want me to prove that's not true?" when a claim about some specific transmasc oppression is made.
And when concrete evidence is given that, e.g. transmasculine people as a class face more sexual violence than transfeminine people, the problem escalates. When we cannot simply be dismissed out of hand as wrong just "because," they have to find another way to discredit us. Since their dismissal of us is based in transphobic bias and not in any real grounding, it's not acceptable for us to prove that we're right about anything. This is where you get situations like r/trans censoring transmascs after one provided citations about violence against us, or people nitpicking studies and claiming their results are biased. It's also often when the slurs come out (if they hadn't already), because there is no greater defense against evidence than to simply stop engaging with reality and call the other person a fembrained theyfab instead.
It's part of a wider pattern, too, not just in interpersonal exchanges. The lies told by the groups oppressing us are taken at face value by the majority of people, including other trans people. "Trans men transition into privilege" and "trans men transition because of internalized misogyny" are literal TERF talking points that are also accepted uncritically as true by a portion of our own community. "AFAB only" spaces are imagined to be havens for transmascs when any of us with experience can tell you what the reality is. People that recognize transphobic lies about trans women willingly swallow those lies whole when they are about trans men.
Even when it isn't straightforward lies told by bigots, people tend to make assumptions about transmascs with no input or research and then treat them like unassailable truth. Writers like Julia Serano simply "suppose" that a person read on the street as transmasculine will face less violence or harassment than someone read as transfeminine. People will confidently say that they "feel like" the stats on violence against trans men must be wrong, based on nothing material. Someone speaking on queer history will do no research into the contributions of transmasculine people, and then assume that we did nothing.
When it comes to the lives and experiences of transmasculine people, anyone and anything, including assumptions, conjecture, feelings, and outright lies, is treated as having more authority than our word.